Mole Concept and Stoichiometry - Scribnotes



Mole Concept and Stoichiometry

• Solve chemical calculations including: particles to moles, mass to moles, volume of a gas to moles

• Solve reaction stoichiometry problems including: moles, mass, and volume of species in a reaction

1. In order to make 12.0 L of 0.250 M HCl.

a) How many moles must be used?

b) How many molecules of HCl must be used?

c) How many grams of HCl must be used?

2. Given 44.8 L of O2 at STP, calculate

a) The number of moles

b) The mass in grams

c) The number of molecules

3. Given 73.0 g of hydrochloric acid and excess zinc, how many liters of hydrogen gas will form at STP?

• Calculate empirical formulas from mass or percent

4. What is the empirical formula for a compound that is 92.3% C and 7.7% H?

5. What is the empirical formula for a compound that has 36.5 g of sodium, 25.4 g of sulfur, and 38.1 g of oxygen?

• Calculate molecular formulas from empirical formulas and molecular wt.

6. What is the molecular formula for a compound with an empirical formula of CoC4O4 and the molecular weight 341.94 g/mol?

• Calculate percent composition of given compounds

7. Determine the percent composition of tin in tin (IV) oxide.

1. The gram formula mass of (NH4)2CO3 is

(A) 46.0 g (C) 78.0 g

(B) 64.0 g (D) 96.0 g

2. Which substance has the greatest molecular mass?

(A) H2O2 (C) CF4

(B) NO (D) I2

3. The total number of moles represented by 20 grams of CaCO3 is

(A) 1 (C) 0.1

(B) 2 (D) 0.2

4. What is the total mass of 2.0 moles of H2 (g)?

(A) 1.0 g (C) 3.0 g

(B) 2.0 g (D) 4.0 g

5. Which sample contains a total of 9.0 x 1023 atoms?

(A) 0.50 mole of HCl (C) 1.5 moles of Cu

(B) 0.75 mole of H2O (D) 1.5 moles of H2

6. What is the total number of atoms contained in a 1.00-mole sample of helium?

(A) 1.00 atom (C) 1.20 x 1024 atoms

(B) 2.00 atoms (D) 6.02 x 1023 atoms

7. What is the total number of nitrogen atoms in 0.25 mole of NO2 gas?

(A) 1.5 x 1023 (C) 3.0 x 1023

(B) 6.0 x 1023 (D) 1.2 x 1024

8. The empirical formula of a compound is CH3. The molecular formula of this compound could be

(A) CH4 (C) C2H6

(B) C2H4 (D) C3H6

9. What is the empirical formula of a compound that contains 30.4% nitrogen and 69.6% oxygen by mass?

(A) NO (C) N2O3

(B) NO2 (D) N2O5

10. A compound consists of 25.9% nitrogen and 74.1% oxygen by mass. What is the empirical formula of the compound?

(A) NO (C) N2O

(C) NO2 (D) N2O5

11. What is the percent by mass of oxygen in propanol, CH3CH2CHO?

(A) 10.0% (C) 38.1%

(B) 27.6% (D) 62.1%

12. In which compound is the percent by mass of oxygen greatest?

(A) BeO (C) CaO

(B) MgO (D) SrO

13. An example of an empirical formula is

(A) CH4 (C) C2H4(OH)2

(B) C2H4 (D) C6H12O6

14. Which molecular formula is correctly paired with its corresponding empirical formula?

(A) CO2 and CO (C) C6H6 and C2H2

(B) C2H2 and CH2 (D) P4O10 and P2O5

15. The volume occupied by 9.03 x 1023 molecules of N2 gas at STP is closest to

(A) 0.500 liter (C) 22.4 liters

(B) 1.50 liters (D) 33.6 liters

16. The total number of molecules in 34.0 grams of NH3 is equal to

(A) 1.00 x 22.4 (C) 1.00 x 6.02 x 1023

(B) 2.00 x 22.4 (D) 2.00 x 6.02 x 1023

17. For the reaction 2Na + Cl2 → 2NaCl, how many grams of chlorine gas are required to react

completely with 2.00 mol of sodium?

|a. |35.5 g |c. |141.8 g |

|b. |70.9 g |d. |212.7 g |

18. For the reaction 2KlO3 → 2KCl + 3O2, how many moles of potassium chlorate are required

to produce 250 g of oxygen?

|a. |2.0 mol |c. |4.9 mol |

|b. |4.3 mol |d. |5.2 mol |

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